Means for reproducing motion



April 15, 1947. J. D. PETERSON ET AL ,419,087

MEANS FOR REPRODUCING MOTION Filed May 28, 1943' 3 Sheets-Sheet 1 RECEWER i. we

INVENTORS F @ezlzruersm BY Rmz KBeckberger.

April 15, 1947. J. D. PETERSON ETAL 2,4 9,087

MEANS FOR REPRODUCING MOTION Filed May 28, 1943 3 Sheets-Sheet 2 All INPUT RECEIVER TRANSMETTEFQ IN V EN TOR$ Joel ilPel'ersom y Fbul FBec/zberger.

P" 1947- J. D. PETERSON ETAL 19 7 MEANS FOR REPRODUCING MOTION Filed May 28, 1943 3 Sheets-Sheet 3 Tutu INVENTORS kel I). Fhbsrsom Paul [I Al'l'orrvy Patented Apr. 15, 1947 MEANS Foa anrnonuomo MOTION Joel D. Peterson, Ridgewood, and Paul F. Bechberger, Tenafly, N. J., assignors to Bendix Aviation Corporation, Bendix, N. 1., a corporation of Delaware Application May as, 1943, Serial No. 488,898

14 Claims. (01. 112-239)..

The present invention relates to means for re- 7 producing motion, and more particularly to novel and improved means for reproducing angular motion at a remote point for indicating and/or control purposes.

It is known in the art to provide a telemetric system comprising two generally similar units, one acting as a transmitter of motion imparted thereto and the other as a receiver for reproducing the exact amount or motion imparted to the transmitter. Illustrative of such known systems, for example, is Patent No. 2,269,602 issued to W. A. Reichel on January 13, 1942, and asfully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein three embodiments of the invention are illustrated by way of example. It is to be expressly understood,v however, that the rawings are for the purposes or illustration only and are not to be construed signed to the assignee of the present invention.

These systems are highly effective where it is practical to use two like units but in some application it is desired to transmit and reproduce motion at a remote point with the use of two dissimilar units. a

An object of the present invention, therefore, is to provide a novel telemetric system wherein the transmitter and receiver units are 01' dissimilar nature.

Another object of the invention is to provide a I system having two units, one acting as a transmitter of motion and the other as a reproducer of motion, one of the units being of the inductive type having a wound stator and a wound rotor, and the: other being an electromagnetic device having a wound stator and an unwound rotor comprising a permanent magnet.

" A f her oblectis to provide a novel telemetric system comprising a transmitter unit dissimilar from the receiver unit wherein the latter unit a may act as an indicator oithe amount of reproduced motion or as a control for a follow-up system.

Another object of the invention is to provide a novel coupling transformer with the use of which a unit having a wound rotor may be coupled with a unit having only a permanent magnet for a rotor to provide a novel motion reproducing system in which either unit may be used as a transmitter or as a receiver.

The foregoing and other objects and advantages of the present invention will appear more as defining the limitsor the invention, reference being'had for this purpose to the appended claims.

In the drawings:

Figure 1 is a more or less diagrammatic illum tration of one embodiment of the invention wherein a transmitter providedwith a perma-- nent magnetic rotor is connected through a novel transformer coupling with a receiver provided with a wound rotor.

Figure 2 is a diagrammatic illustration of another embodiment of the invention in which the receiver of Figure 1, is used as the transmitter and the transmitter of- Figure 1 is used as the receiver.

Figure 3 is a diagrammatic illustration of a further embodiment of the invention wherein the arrangement of Figure l is adapted as a control for a follow-up system.

The invention consists substantially in the construction, combination, location and relative arrangement or parts and circuits for obtaining the results desired in accordance with the foregoing objects, as will be more fully. hereinafter set forthin the specification, as shown in the drawings by way of example, and as finally pointed outin the claims.

Referring now to the drawings and more particularly to Figure 1 thereof, the novel apparatus of the present invention comprises, in the form shown, a transmitter 5, constituting one type r an electro-magnetic unit, electrically connected through a novel coupling transformer, to be described more fully hereinafter, with a receiver 8 which is a distinctly difierent type of a unit from transmitter 5. It will be apparent that two or more receivers may be provided for reproducing the motion of the transmitter.

The transmitter is of the type shown and described in the copending application Serial No. 410,343 filed Septemberli), 1941, now Patent No. 2,342,637 issued February 29, 1944, and assigned to the assignee of the present invention, and comprises a stator and a rotor in cooperative relation therewith, the stator consisting of a core I formed as a laminated ring of highly permeable magnetic material such, for example, as Permalloy" or Mumetal," having wound thereon a single Winding or coil 6 which is tapped at two or more points as, for example, at points I and II, intermediate the ends II and II of the coil,

\ the ends thereof and the tapped points being an gularly spaced one hundred twenty degrees (120) apart along core I.

Mounted concentrically within stator core I of the transmitter and in magnetic relation therewith, as well as with coil I, is a rotor element II in the form of a magnetic member of marked polarity as, for example, a rotatable permanent magnet having north and south poles as indicated at N and S, providing a uni-directional magnetic flux which enters core I. The rotor element is shown in the form of a disc magnet, onehalf of which constitutes the north pole and the other half the south pole.

The motion of the transmitter unit, above described, is to be reproduced by a receiver unit entirely diflerent from the transmitter. As shown in Figure 1, receiver I is located at a remote point and comprises an induction device of the rotary transformer type having a stator element provided with three windings II, II and II connected in three-phase relation at Junction I1, and a rotor element, adapted for angular movement relative to the windings, having a single phase winding II arranged in inductive relation with the three phase connected windings Due to the fact that the transmitter unit is of one type utilizing a single winding having therein an energizing current flow of fundamental frequency and the receiver of another and diflerent type, the two units cannot be connected with each other directly because, in addition to the generated secondary harmonic in the tapped portions of the transmitter winding, there is the fundamental component which must be balanced or made ineffective. A novel coupling transformer unit, generally designated at II, to be described in detail presently, is provided whereby the fundamental component is eliminated and motion of the transmitter is accurately and rapidly reproduced by the receiver.

Current for energizing winding I of the transmitter stator is supplied by mains or conductors III and II which connect with a suitable source (not shown) of alternating current or pulsating direct current, the winding being tapped to the supply mains at 22 and II. As explained in connection with a similar unit shown by the above referred to copending application Serial No. 410,343, secondary voltages are generated in the tapped sections of winding I due to the periodic reversal of the flux produced in core I by the periodically varying current flowing in the winding; During one-half cycle of the exciting current flowing in winding I, the periodically varying flux-opposes the uni-directional flux of the rotor in one half of core I and, at the same time, aids the uni-directional flux in the other half of the core, while during the other half of the cycle of the exciting current the periodically varying flux aids the uni-directional flux of the rotor in the first-mentioned half of the core and, at the same time, opposes the uni-directional flux in the other half of the core. Thus the winding I has a current of fundamental frequency flowing therein as well a secondary harmonics and upon relative movement of therotor the amount or value of the second harmonics thus generated in the tapped sections of the winding is varied.

Coming now to the novel coupling means for interconnecting transmitter. I with receiver I, which comprises transformer II of Figure l, the

latter is shown as having a Primary winding II connected across mains II and II and having inductively associated therewith secondary windings II and II, the latter being wound in opposition ,to the former. One side of the secondary II is connected by way of a lead I! with tapped point I of the energizing winding I while the other sIde of the same secondary connects by way of a conductor II with the free end of stator winding II of the receiver. In a like manner. one side of secondary winding II connect with tapped point II of winding I by way of a suitable conductor I9 while the opposite end of the secondary connects through a lead II with the free end of stator winding II of the receiver. On the other hand, the free end of stator winding II of the receiver connects by way of a lead II with a central tap on the primary winding.

The primary and secondary windings of transformer II are so designed that each of the secondaries produces one-sixth of the input voltage of mains II and II. For purposes of explanation, only the input voltage across mains II and II will be considered to the exclusion of the secondary harmonics, and for simplicity the voltage may be taken as having a value of six volts. Since receiver stator winding II is tapped to primary II at a central point thereon, the potential of connecting lead II as well as winding II will be three volts. Tapped point I of winding I, being located one third the distance of the winding, has

4 a potential or two volts. By virtue of the transformer action, secondary winding II will have one volt induced therein so that the potential of lead II as well as winding II will also be three volts. Tapp d point II, on the other hand, being located two thirds the distance of winding I, will have a potential of four volts. Secondary winding II. connected to tapped point II by virtue of lead II, i arranged oppositely to secondary II so that there will be a potential drop of one volt, making the potential of lead II and winding II three volts.

Thus the fundamental components present in coil I are eliminated by transformer II so that only the secondary harmonics will act to control rotor winding II of the receiver. By virtue of the novel transformer coupling, two substantially dissimilar units are brought together to provide a new and novel telemetric system. I

Means are now provided for angularly moving transmitter rotor II in accordance with and hi response to the factor to be measured and to be indicated at the remote. or distant receiver in substantially the same manner as disclosed in the aforementioned application Serial No. 410,343. Such means may comprise, as shown, a drive shaft II having one end connected to rotor II and carrying at its other end a pinion II mashing with a gear sector II which is pivoted at II and connected to a measuring instrument such, for example, as an evacuated bellows or altimeter aneroid II by means of a link I1 and a lever II. It will be obvious that throuch the connection described, expansion or contraction of cisment II will causorotor lltnturninaclockwise or counterclockwise direction.

Rotor-winding ilisdrivablyconnectedina suitable manner with a pointer II for angular movement over a seals II so that motion imparted to transmitter rotor II is reproduced in value and direction by receiver rotor II which moves pointer II'rciative to scale II to indicate the amount M motion transmitted.

For a condition of synchronism wherein rotor "and rotor winding I8 are balanced or :In step,

fundamental component of the input current as well as secondary harmonics are present 'inithe as has already been shown, the eflect'of the fundamental components is eliminatedby transforme1- I8 so that only the secondary harmonics-are present in stator windings I4, I5 and 18. .As soonas the-value or effect of the conditionbeing measured atthe transmitter is changed, aneroid136 responds to the change and angularly displaces rotor I3 relative to its winding-8 and the values of-the second harmonic at each :of the tappedsections of winding 8 are changed. B alance no longer exists between the transmitter and receiver rotors so that the valuesof the second harmonics at the receiver stator windings are likewise changedthereby displacing the resultant vflux vector at the receiver stator.

Because of the fact that the flux within core I reverses its direction twice for each cycle of the energizing ,field by virtue of its connection by way of leads 1 4| and 42 with the input current source. As pointed outabove the secondary currents within 'the stator have a frequency double the frequency of the input currentso that a suitable and known frequency doubler 48 must be interposed between the receiver rotor winding I8 and the mains and 2|. To this end the input of doubler 43 is connected with mains 20 and 2| by wayof leads 44 and 45 while the output thereof connects with leads .4I and 42. The magnetic field of winding I8 reacts with the displaced flux vector at the receiver stator so that a torque is generated moving winding I8 to a null or in step position with rotor I8 at which time pointer 38 is moved relative to scale 40 to thereby indicate the amount of change of the condition being measured at the reproduce and indicate the amount of motion imparted tothe transmitter. The receiver rotor is supplied with twice the frequency of the trans- -a core I0'I of highly permeable material'having wound thereon a'single'winding'or coil 108 tapped at points I08 and H0, the end and tapped points beingangularly spaced T0116 hundred and twenty degrees (120?) 'apart about core I01. Mounted concentrically withinicore 101 Star: angular movement relative to .the-tcore 'andxits 'winding is a permanent "magnet 110 which may be connected through suitabl'e means with'a rpointer 188 superimposed for movement rover rascale 140. Rotor I I'3.-is shown in the "form ofa-"disc magnet,

one half of which' constitutes iasnorth ;-pole and.

theotherhalfasouth pole, marked Nzand S, respectively,iin Figure 2.

The ends-of winding I08 are-connected at taps I22 and I28 forenerg'ization with supply mains I20 and .121 which are connected to ausuitable source '(notshown) ofalternating current-orpulsatingdirect'current. As *pointedout in connection with the description -01 Figure '51, the .flux traversing core .-I0I willreverse :its direction twice for each :cycle of the energizing current or mains I20 and 'I2I so thatsecondary voltasesiinducedin winding I08 will have a frequency twice the frequency'of theinputcurrent. :Since the secondary voltages at'the receiver aretwice-theifrequency of the input voltage, a suitable frequency doubler I48 has its outputconnected to'rotor winding I I8 by way of leads I4 I and I42 and its input to mains I20 and I2I by waygof'leads I144;an'd 148. Thus, the current in rotor winding 5H8 has a frequency double the frequency of the iinput'current,

Since, in addition to the second Lharmonics, fundamental components of the energizing "current are present in the receiver :s'tator winding I08, the novel transformer of Figure 1 is interposed between the receiver and transmitter to eliminate the fundamental components so that only the secondaryJharmonics' will be present within stator windings 114, I I8 and I I8. To this end primary winding I24 of transformer H9 is connected across mains I20 and I21 :while winding I I501 thetransmitter stator is connected by way of a lead I81 to a central point'on winding I24. The transformer is i'urtherprovided with two secondary windings I25 and I26, one of whichis wound in opposition to the other. Secondary I28 is connected atone end with stator winding II4 mitter input and is under the complete controi of the secondary signal from the transmitter.

oi' Figure 1 will be used as the receiver. To this end the arrangement of Figure 2 is provided and by way of a'lead I21 and with tapped point I08 of stator winding I08 by way of a lead I28 while secondary I26 is connected atone end with windoomprises as shown a transmitter I08, similar to receiver 8 of Figure 1, having a stator'provided with three windings I I4, H8 and H6 connected in three-phase relation at Junction I I1, and a rotor element, adapted for angular movement, having a single-phase winding 1 I8 arranged in inductive relation with the three-phase connectedwindingslll, us and us.

ing N6 of the transmitter stator by way of a lead I 29 and at its other end with tapped point IIO by way of lead "I80. In this manner fundamental components are eliminated from windings H4, H5 and I I6 so that only the generated -second harmonics are present within the transmitter stator.

.f'in'g II8 changes the values of the second harmonies generated within thestator windings, the

In a manner similar to that shown in Figure 1,

means are provided for rotating winding H8 in accordance with the amount of change of the I condition measured which comprises a drive shaft I82 having one end connected to rotor winding H8 and carrying at its other end a pinion I88 meshing with a gear sector I34 which is pivoted induced voltage in each winding varying in accordance with the angular position of rotor winding I I8, The values of the secondary voltages are thus changed at the tapped portions of receiver stator winding I08 whereby the resultant flux vector at the receiver is moved so that it reacts with the magnetic field of the receiver rotor to produce a torque which causes the magnet rotor to turn angularly and bring it into positional agreement with the transmitter rotor. Rotation of the rotor actuates pointer I88 relative to scale 4 I40 toshow the amount of angular displacement of transmitter rotor I I8 in response to a change in the condition being measured by aneroid I36.

In the foregoing manner a novel telemetric system is provided in which the receiver unit of Figure 1 is used as the transmitter and the transmitter of Figure 1 becomes the receiver.

In some cases it is desirable to create sufilcient torque at the receiver to actuate a control surface, valve or other element in accordance with the amount or value of the motion imparted to the transmitter. In such an event the torque generated at the receiver must be amplified and one method of accomplishing this purpose is by providing a follow-up motor which, in bringing the receiver rotor to a null or positional agreement with the transmitter, will also operate the control desired. To this end, therefore, the structure of Figure 3 is provided and, as there shown, the system is essentially the same as that of Figure 1 and all parts corresponding to like parts in Figure 1 are designated with the same reference character plus 200.

Thearrangernent of Figure 3 difiers from the arrangement of Figure 1 in that in the former the receiver rotor, of itself, is incapable of seeking a null or positional agreement with the transmitter rotor once a condition of synchronism has been destroyed. Motion on the part of the transmitter, therefore, results in a change in the secondary voltages at receiver stator windings 2, H and H6, as described in connection with Figure 1, so that a signal is induced in rotor winding U8. The signal so induced is fed to the input of a conventional amplifier 250 by way of leads 25I and 252, the output thereof being connected by way of leads 253 and 254 with one phase 255 of a twophase induction motor, generally designated at 258, and having a rotor 251. The second phase 258 of the motor is connected for constant energization with mains 220 and 22! through a frequency doubler 243, the latter having its input connected to the mains by way of leads 2 and 245 and its output by way of leads 259 and 260 with the second phase of the motor.

The rotor 25'! is mechanically coupled through a suitable reduction gearing 26! and a shaft 262 with rotor winding M8. The latter in turn is mechanically coupled with a suitable pointer 239 superimposed for movement over a scale 240. In order that the currents in phase 255 will be 90 out of phase with the current in phase 258 a. suitable condenser 263 is provided at the amplifier output.

With the expansion or contraction of aneroid 236, in response to a change in the condition 1 being measured, transmitter rotor 2| 3 is displaced angular-1y changing the values of the secondary currents at the tapped sections of the stator coil which change is communicated to stator windings 2H, 2|5 and 2| 5 of the receiver. The resultant flux vector at'the receiver stator is no longer normal to rotor winding 2l8 so that a current is induced to flow therein which is amplified by amplifier 250 and fed into second phase 255 of the motor. The second phase 258 being already energized, rotor 25! is turned and through gearing 26! and shaft 262 drives the rotor winding 2l8 until the latter reaches a null, i. e., the wind ing assumes a position normal to the resultant flux vector at the receiver stator, at which time the induced signal within winding 2| 8 becomes zero and phase 255 is de-energized. At the same time pointer 239 has been moved relative to scale 2 to indicate the amount of change at the transmitter while any desired control element may be coupled to motor 258 to be actuated thereby in accordance with the change at the transmitter.

Although the transmitter units 5 and 205 of Figures 1 and 3 have been shown as having permanent magnet rotors l3 and 2H! actuated by anerolds 36 and 236 it is to be understood that the magnetic rotors shown may be replaced by a magnetic or earth inductor compass as disclosed in the aforementioned application Serial No. 410,343. Moreover, even though rotors l8, H8 and 2! of the inductive devices have been shown a wound, they may be of the unwound type,

to indicate the amount of change at a distant point without the use or a follow-up motor or may include such a motor when a relatively greater amount of torque is desired.

Although three embodiments of the invention have been illustrated and described in detail,

various changes and modifications in the construction and relative arrangement of the parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is therefore to be had to the appended claim for a definition of the limits of the invention.

We claim:

1. Means for transmitting motion from one point to another and 'diflerent point including a transmitter unit and a. receiver unit, one of said units comprising annular core means of magnetically permeable material arranged to be traversed by a magnetic field for inducing a magnetic flux therein and provided with coil means thereon whereby secondary harmonics are generated therein due to said magnetic flux, the other of said units comprising a wound stator and a rotor in inductive relation with the stator, a source of periodically varying input current connected to said coil means whereby fundamental components of the input current are induced in said coil means, and transformer means for eliminating said fundamental components comprising a primary winding connected to said current source and opposed secondary windings for interconnecting said coil means with said wound stator.

2. Means for transmitting motion from, one point to another and diflerent point including a transmitter unit and a receiver unit, one of said units comprising annular core means of magnetically permeable material arranged to be traversed by a magnetic field for inducing a. magnetic flux therein and provided with coil means thereon whereby secondary harmonics are generated therein due to said magnetic flux, the other of said units comprising a wound stator and a wound rotor in inductive relation with the stator, a source of periodically varying input current connected to said coll means of said one unit and to said wound rotor of said other unit whereby fundamental components of the input whereby secondary harmonics are generatedtherein due to said magnetic flux, the other of said units comprising a wound stator and a wound rotor in inductive relation with the stator, a source of periodically varying input current connected to said coil means of said one unit and to said wound rotor of said other unit, whereby fundamental components of the input current are induced in said coil means, and transformer means having a primary winding connected to said current source and a pair of oppositely wound secondary windings, said coil means and said wound stator being interconnected through said secondary windings whereby fundamental components of the input current are eliminated so that only the secondary harmonics are present in said wound stator.

4. Means for transmitting motion from one point to another and different point including a transmitter unit and a receiver unit, one of said units comprising core means of magnetically permeable material arranged to be traversed -by a magnetic fieldfor inducing a magnetic flux therein and provided with coil means thereon and having an input and a plurality of tapped sections, said coil means having secondary harmonics generated therein due to said ma etic flux, the other of said units comprising a stator having a plurality of windings arranged in threephase relation and a wound rotor in inductive relation with said stato a source of periodically varying input current connected to the input of said coil means and .to said rotor whereby funhaving a primary connected to said current source and a pair of oppositely wound secondary windings, one of said stator windings being connected to a central portion of said transformer primary and the remainder of said stator windings being connected through said transformer secondary windings with the tapped sections of said coll means.

6, A repeater system comprising a transmitter unit having an annular core member of magnetically permeable material, means arranged concentrically with said core member for relative movement thereto and providing a unidirectional magnetic field induced in said core member, coil means on said core member having generated therein secondary harmonics due to said induced magnetic field and having an input and a plurality of tapped outlet connections, a receiver unit having a stator provided with a plurality of windings thereon, a rotor member in inductive relation with said stator windings, a source'of periodically varying input current connected to the input or said coil means whereby fundamental components of the input current are generated in said coil means, and a transformer comprising a primary winding connected with said current source and having opposed secondary windings for interconnecting the tapped outlet connections or said coil means with the windings of said stator whereby the fundamental components of the input current induced in said coil means are eliminated.

7. A repeater system comprising a transmitter unit having an annular core member of magnetically permeable material, a permanent magnet arrangedconcentrically with said core member for relativemovement thereto and providing a unidirectional magnetic fleld'induced in said core member, coil means on said core member having generated therein secondary harmonics due to said induced magnetic field and having an input and a plurality of tapp d output connections; 9. receiver unit having a stator'provided with a plurality of windings thereon, a wound rotor member in inductive relation with said stator windings, a source of periodically varying input current connected to the input of said coil damental components of the input current are] induced in said coil means, and a transformer having a primary connected with said current source and a pair or oppositely arranged secondary windings, one of said stator windings being connected to a central portion of said transformer primary and the other of said stator windings being connected through said transformer secondary windings with the tapped sections or said coil means whereby the fundamental components of the input current are eliminated so that only the secondary harmonics 'act withg in the stator windings. r

5. Means for transmitting motion from one point to another and different point including a transmitter unit and a receiver unit, one of in'said core member, coil means on said core said units comprising core means of magnetically permeable material arranged to be traversed by a magnetic field for inducing a magnetic flux therein and provided with coil means thereon and having an input and a plurality of tapped sections, the other of said units comprising a stator having a plurality of windings arranged in three-phase relation and a wound rotor in inductive relation with said stator, a source of periodically varying input current connected to the input of said coil means and to said rotor, a frequency doubler interposed between said current source and said rotor, and a transformer means and to said wound rotor member whereby fundamental components of the input currentare generated in said coil means, and a transformer comprising a primary winding connected to said current source and opposed secondary windings for interconnecting the tapped output connections of saidcoii means with the windings of said stator.

8. A repeater system comprising a transmitter f unit having an annular core member of magnetically permeable 'material, a magnet arranged for movement relative to said core member and providing a unidirectional magnetic field-induced member having generated therein secondaryhar. monics due to said magnetic field and having an input and a plurality of tapped output connections, 9. receiver unit having a stator provided with a plurality of windi'ngs' 'thereomq'aj .rotor memberv comprising a single windinginiinduc' tive relation with. said'stator windingsfa somicefof periodically varying current connecte'd" to the input of said coil means and to saidrotor wind-. a ing whereby fundamental components'pfjthe in put current are generated in said :coll'cmesn's; a;- transi'ormer comprising a primary winding con- 1' nected to said current source and having opposed secondary windings for interconnecting the tapped output connections of said coil means with the windings of said stator so that the fundamental components of the input current are eliminated and only secondary harmonics act within said stator windings, the value of the secondary harmonics within said stator windings being changed upon relative movement of said magnet so that a voltage is induced in said rotor winding, and means comprising a follow-up motor connected with said rotor and energized by the voltage induced in said rotor winding.

9. A repeater system comprising a transmitter unit having core means of magnetically perme able material arranged to be traversed by a r latively movable magnetic field for inducing a magnetic flux therein and provided with coil means thereon having an input and output connections, said coil means having secondary harmonies generated therein due to the magnetic flux induced in said core means, a receiver unit having a wound stator and a rotor comprising a single winding in inductive relation with said stator, a source of periodically varying current connectedto the input of said transmitter coil means and to said receiver rotor winding whereby fundamental components of the input current are induced in said coil means, a transformer comprising a primary winding connected to said current source and having opposed secondary windings for interconnecting the output connections of said coil means with the stator windings so that the fundamental components of the input current are eliminated and only secondary harmonies act within said stator windings, the value of thesecondary harmonics within said stator windings being changed upon relative movement of said magnetic field so that a voltage is induced in said rotor windings, and means comprising a follow-up motor connected with said rotor and energized by the voltage induced in said rotor winding.

10. A repeater system comprising a transmitter unit having annular core means of magnetically permeable material arranged to be traversed by a relatively movable magnetic field for inducing a magnetic flux therein and provided with coil means thereon having an input and output connections, said coil means having. secondary harmonies generated therein due to said magnetic flux, a' receiver unit having a stator provided with a plurality of windings thereon and a wound rotor member in inductive relation with said stator windings, a source of periodically varying current connected to the input of said transmitter coil means and to said wound rotor member whereby fundamental components of the input current are induced in said coil means, and transformer means comprising a primary winding connected with said current source and having opposed secondary windings for interconnecting the output connections of said coil means with the windings of said stator for eliminating said fundamental components.

11. In combination, a transmitter comprising core means of magnetically permeable material arranged to be traversed by a unidirectional magnetic field for inducing a magnetic flux therein and provided with coil means thereon having an input and a plurality of output connections, said coil means having secondary harmonics generated therein due to said magnetic flux, a receiver having a stator provided with a plurality of windings thereon, a wound rotormember in inductive relation with said stator windings, a source of periodically varying input current connected to 12 the input of said cell means and to said rotor member whereby fundamental components of the input current are generated in said coil means,

and transformer means having a primary winding connected to said current source and a pair of 1 oppositely wound secondary windings, the output connections of said coil means being connected with one of the ends of the secondary windings and the stator windings being connected to the other of the ends of the secondary windings so that the fundamental components of the input current are eliminated and only second harmonic; act within the stator windings.

12. In combination, a transmitter comprising a stator provided with a plurality of windings thereon, a wound rotor member in inductive relation with said stator windings, a receiver comcurrent source and having opposed secondary prising core means of magnetically permeable material arranged to be traversed by a relatively movable unidirectional magnetic field for inducing a magnetic flux therein and provided with coil means thereon having an input and plurality of other connections, said coil means having generated therein secondary harmonics due to said magnetic flux, a source of periodically varyin current connected to the input of said coil 4 means and said rotor member whereby fundamental components of the input current are in. duced in said 0011 means. and a transformer comprising a primary winding connected with said windings for interconnecting said stator windings with the other connections of said coil means whereby fundamental components of the input current are eliminated.

13. A repeater system comprising a transmitter having a stator provided with a plurality of windings thereon, a wound rotor member in inductive relation with said stator windings, a receiver having a core member of magnetically permeable material, means arranged concentrically with said core memberv for relative movement thereto and providing a unidirectional magnetic field induced in said core member, coil means on said core member having generated therein secmdary harmonics due to said magnetic fleld'and having an input and a plurality of tapped connections,

a source of periodically varyingcurrent connected to the input of said coil means and to said rotor member whereby fundamental components of the input current are induced in said coil means, and a transformer having a primary winding connected with said current source and opposed secondary windings for interconnecting the stator windings with the tapped connections of said coil means whereby fundamental components of the input current in said coil means are eliminated so that only secondary harmonics act in said stator windings.

14. A repeater system comprising a transmitter having a stator provided with a plurality of windings thereon, a woundrotor member in inductive relation with said stator windings, a receiver having a core member of magnetically the stator winding; with the tapped connections I of said coil means whereby fundamental components of the input circuit induced in said coil means are eliminated so that only secondary harmonics act in said stator windings.

JOEL D. PETERSON. PAUL F. BECHBERGER.

14 nmmmcss crisp The following references are of'record in the Number y me of this patent:

UNITED s'rs'rns rs'rnm Name Date lReichel Jan. 13, 1942 Peterson July 6, 1943 Stuart Mar. 9, 1943 Noxon Jan. 19, 1943 La Pierre a 5cm. 1, 1936 

